Lipase Enzyme Immobilized Magnetic Nanoadsorbent: A Promising Candidate to Efficiently Remove Chromium from Aqueous Media

The Enzyme-immobilized magnetic nanocomposites as a nano adsorbent are interested in the environmental fields and energy science due to their number of advantages including high surface area, biocompatibility, ease of separation, reusability, and substantial activity. The Lipase enzyme (Candida rugosa) was immobilized onto a lipase-immobilized magnetic nanocomposite (Fe3O4@SiO2-NH2) using a chemical dispersion method under constant stirring to effectively adsorb Chromium (VI) from aqueous media. After successful immobilization, the lipase@ Fe3O4@SiO2-NH2 nanocomposite was characterized using various analytical instruments. Fouriertransform infrared (FTIR) analysis, scanning electron microscopy (SEM), Zeta sizer, Zeta potential, Brunauer Emmett-Teller (BET) analysis, and X-ray diffraction (XRD) were utilized to characterize the surface modification, structure, super magnetic properties, pore size, and chemical content within the synthesized magnetic nanocomposite and its variants. To evaluate the adsorption capability of the newly synthesized nanocomposite, batch adsorption experiments were performed under the influence of various controlled parameters. The batch adsorption trials revealed that pH significantly influenced the adsorption of Cr (VI). At a pH level of 2.0 and a temperature of 318 K, the maximal adsorption capacity reached 49.9 mg/g, with the isotherms fitting the Freundlich model and the Pseudo-second kinetic model. The thermodynamic study demonstrates the exothermic and spontaneous nature of Cr (VI) adsorption on the adsorbent (lipase @ Fe3O4@SiO2-NH2). Additionally, the adsorbent exhibited good reusability, and Cr (VI) ions could be successfully desorbed using a solution of 0.1 mol/ L NaOH. The synthesized nanocomposite demonstrated validity and applicability in real water samples, achieving mean removal efficiencies of tap water, Nawab Shah Canal, and Hyderabad Canal were 94.92 +/- 3.12, 95.80 +/- 2.78, and 96.81 +/- 2.58 %. The lipase @ Fe3O4@SiO2-NH2 nanocomposite reveals a promise as an efficient nano adsorbent for the adsorption of Cr (VI). Moreover, the maximum lipase enzyme immobilization activity was observed at 20 mg/g in water (pH 8) at 25 degrees C. Fabrication of the lipase@ Fe3O4@SiO2-NH2 is illustrated in the graphical abstract of the manuscript.